High linear density tunnel junction flux guide read head with in-stack longitudinal bias stack (LBS)

ABSTRACT

Several embodiments of a sense current perpendicular to the planes of the sensor (CPP) and flux guide type of read head has a gap between first and second shield layers at an air bearing surface (ABS) where the flux guide is located which is less than a gap between the first and second shield layers at a recessed location where the sensor is located. This reduced gap increases the linear bit density capability of the read head. A longitudinal bias stack (LBS) is located in the sensor stack. Several unique methods of construction are described for forming the magnetic head assemblies.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a high linear density tunnel junctionread head with in-stack longitudinal bias stack (LBS) and, moreparticularly, to such a read head wherein the gap at an air bearingsurface, where the flux guide is located, is smaller than the gap of atunnel junction read head which is recessed from the ABS.

2. Description of the Related Art

The heart of a computer is a magnetic disk drive which includes arotating magnetic disk, a slider that has read and write heads, asuspension arm above the rotating disk and an actuator arm that swingsthe suspension arm to place the read and write heads over selectedcircular tracks on the rotating disk. The suspension arm biases theslider into contact with the surface of the disk when the disk is notrotating but, when the disk rotates, air is swirled by the rotating diskadjacent an air bearing surface (ABS) of the slider causing the sliderto ride on an air bearing a slight distance from the surface of therotating disk. When the slider rides on the air bearing the write andread heads are employed for writing magnetic impressions to and readingmagnetic field signals from the rotating disk. The read and write headsare connected to processing circuitry that operates according to acomputer program to implement the writing and reading functions.

An exemplary high performance read head employs a tunnel junction sensorfor sensing the magnetic field signals from the rotating magnetic disk.The sensor includes a tunneling barrier layer sandwiched between aferromagnetic pinned layer and a ferromagnetic free layer. Anantiferromagnetic pinning layer interfaces the pinned layer for pinningthe magnetic moment of the pinned layer 90° to an air bearing surface(ABS) wherein the ABS is an exposed surface of the sensor that faces therotating disk. The tunnel junction sensor is located betweenferromagnetic first and second shield layers. First and second leads,which may be the first and second shield layers, are connected to thetunnel junction sensor for conducting a tunneling current therethrough.The tunneling current is conducted perpendicular to the major thin filmplanes (CPP) of the sensor as contrasted to a spin valve sensor where asense current is typically conducted in (parallel to) the major thinfilm planes (CIP) of the spin valve sensor. However, a spin valve sensorcan be arranged so that the current is conducted perpendicular to theplane. Although the description below pertains to a tunnel junctionsensor, the invention can also be employed with CPP spin valve sensors.A magnetic moment of the free layer is free to rotate upwardly anddownwardly with respect to the ABS from a quiescent or zero bias pointposition in response to positive and negative magnetic field signalsfrom the rotating magnetic disk. The quiescent position of the magneticmoment of the free layer, which is parallel to the ABS, is when the biascurrent is conducted through the sensor without magnetic field signalsfrom the rotating magnetic disk. The sensitivity of the tunnel junctionsensor is quantified as magnetoresistive coefficient dR/R where dR isthe change in resistance of the tunnel junction sensor from minimumresistance to maximum resistance and R is the resistance of the tunneljunction sensor at minimum resistance.

In the prior art, the first and second shield layers or first and secondlead layers may engage the bottom and the top respectively of the tunneljunction sensor so that the first and second shield layers or the firstand second lead layers conduct the bias current through the tunneljunction sensor perpendicular to the major planes of the layers of thetunnel junction sensor. The tunnel junction sensor has first and secondside surfaces which are normal to the ABS. First and second hard biaslayers abut the first and second side surfaces respectively of thetunnel junction sensor for longitudinally biasing the magnetic domainsof the free layer. This longitudinal biasing stabilizes the free layerand maintains the magnetic moment of the free layer parallel to the ABSwhen the read head is in the quiescent condition.

Except for the first and second shield layers, the flux guide istypically constructed separately from the tunnel junction sensor inorder to satisfy the location of the flux conducting layer and one ormore insulation layers. Typically, the first and second shield layers ofthe flux guide sensor are extensions of the first and second shieldlayers for the tunnel junction sensor. Accordingly, the first and secondshield layers for the flux guide sensor at the ABS typically have thesame gap therebetween as the first and second shield layers at thetunnel junction sensor. This means that the gap between the first andsecond shield layers at the ABS, and therefore the linear density of theread head, is controlled by the sensor stack which includes all of theaforementioned layers as well as a cap layer and first and second leadlayers if they are employed with the sensor. With the demand for highlinear density read heads, this is a serious design restriction. Itshould be understood that an increase in the linear density of the readhead means that more bits per inch can be read by the read head alongthe circular track of the magnetic disk which permits an increase in thestorage density of a magnetic disk drive.

SUMMARY OF THE INVENTION

The present invention provides a tunnel junction flux guide read headwhich has a smaller gap between the first and second shield layers atthe ABS, as compared to the gap between the first and second shieldlayers at a recessed tunnel junction sensor. This has been accomplishedby extending the free layer of the tunnel junction sensor to the ABS sothat the extended free layer serves as the flux conducting layer of theflux guide along with sloping the second shield layer downwardly as itextends from the tunnel junction sensor to the ABS so that the gapbetween the first and second shield layers at the ABS is less than thegap between the first and second shield layers at the tunnel junctionsensor. The sloping of the second shield layer is permitted by employingan insulation layer which has a thickness that is less than the totalthickness of milled-away pinning, pinned and spacer layers of the tunneljunction sensor. Depending upon whether the tunnel junction sensor is atop free layer located type of sensor or a bottom free layer locatedtype of sensor, a unique method of construction is employed forproviding the free layer extension to the ABS and sloping the secondshield layer downwardly so as to decrease the gap between the first andsecond shield layers at the ABS.

In our invention, the longitudinal bias field is provided by an in-stacklongitudinal bias stack (LBS).

Combining this scheme for longitudinal stabilization and the flux guidefor preventing shorts between the free and pinned layer, we are able toobtain a gap at the ABS which is much smaller than that of the wholesensor stack so that the invention provides a method for making a narrowgap sensor and enhances the read head linear density. The advantage ofthis approach can be illustrated by the following: in-stack longitudinalbias has an advantage for improving a sensor's permeability. However, itwill increase the total thickness of the sensor at the ABS, i.e. 350 Åfor tunnel junction+100 Å for the in-stack, wherein the in-stack biasincludes a spacer (20 Å), a longitudinally biased layer, LBL (30 Å) andan antiferromagnetic (AFM) layer (50 Å), so that the thickness of thesensor=350+100=450 Å. The gap is limited by the sensor thickness.However, by using the invention, the part of the sensor at the ABS, thefree layer (30 Å) plus the in-stack (100 Å) is only 130 Å.

An object of the present invention is to provide a tunnel junction fluxguide read head which has a smaller gap at the ABS where a flux guide islocated as compared to the gap at a recessed tunnel junction read head.

Another object is to provide various methods of making theaforementioned tunnel junction guide read head, depending upon whether atunnel junction sensor is a top located free layer type of sensor or abottom located free layer type of sensor.

Other objects and attendant advantages of the invention will beappreciated upon reading the following description taken together withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an exemplary magnetic disk drive;

FIG. 2 is an end view of a slider with a magnetic head of the disk driveas seen in plane 2—2 of FIG. 1;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is an ABS view of the magnetic head taken along plane 5—5 of FIG.2;

FIG. 6 is a partial view of the slider and a merged magnetic head asseen in plane 6—6 of FIG. 2;

FIG. 7 is a partial ABS view of the slider taken along plane 7—7 of FIG.6 to show the read and write elements of the merged magnetic head;

FIG. 8 is a view taken along plane 8—8 of FIG. 6 with all material abovethe coil layer and leads removed;

FIG. 9 is a cross-section of sensor material layers which have beenformed on a wafer (not shown);

FIG. 10 is a top view of the sensor material layers with a mask formedthereon for defining a sensor stripe height;

FIG. 11 is a view taken along plane 11—11 of FIG. 10;

FIG. 12 is the same as FIG. 11 except the mask has been removed, the caplayer has been etched away and an alumina layer has been formed;

FIG. 13 is the same as FIG. 12 except a second free layer and a secondlead layer have been formed;

FIG. 14 is a top view of FIG. 13 after a mask has been formed fordefining the track width of the sensor;

FIG. 15 is a view taken along plane 15—15 of FIG. 14;

FIG. 16 is a block diagram illustrating the removal of the mask in FIG.15 and the deposition of the second shield layer;

FIG. 17 is a top view showing formation of the third mask on top of thesecond shield layer for defining the stripe height of the flux guide;

FIG. 18 is a block diagram illustrating ion milling about the mask inFIG. 17 and the removal of the mask;

FIG. 19 is a top view after lapping to the ABS;

FIG. 20 is a view taken along plane 20—20 of FIG. 19;

FIG. 21 is a cross-section through another plurality of sensor materiallayers which are deposited on a wafer (not shown);

FIG. 22 is a top view of the sensor material layers with a first maskformed thereon for defining a stripe height of the flux guide;

FIG. 23 is a block diagram showing ion milling of the cap, depositingalumina and removing the first mask;

FIG. 24 is a cross section through the sensor material layers after thesteps in FIG. 23;

FIG. 25 is a top view of FIG. 24 after forming a second mask fordefining a track width of the read head;

FIG. 26 is a view taken along plane 26—26 of FIG. 25;

FIG. 27 is a top view of FIG. 26 after removal of the second mask andformation of a third mask for forming a stripe height of the sensor;

FIG. 28 is a view taken along plane 28—28 of FIG. 27;

FIG. 29 is a block diagram showing removal of the third mask in FIG. 28and depositing the second lead and the second shield layer;

FIG. 30 is a top view after lapping to form the ABS;

FIG. 31 is a cross-section of the final structure after lapping;

FIG. 32 is an ABS view of one embodiment of the LBS;

FIG. 33 is an ABS view of another embodiment of the LBS; and

FIG. 34 is an ABS view of still another embodiment of the LBS.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Magnetic Disk Drive

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views, FIGS. 1-3 illustratea magnetic disk drive 30. The drive 30 includes a spindle 32 thatsupports and rotates a magnetic disk 34. The spindle 32 is rotated by aspindle motor 36 that is controlled by a motor controller 38. A slider42 has a combined read and write magnetic head 40 and is supported by asuspension 44 and actuator arm 46 that is rotatably positioned by anactuator 47. A plurality of disks, sliders and suspensions may beemployed in a large capacity direct access storage device (DASD) asshown in FIG. 3. The suspension 44 and actuator arm 46 are moved by theactuator 47 to position the slider 42 so that the magnetic head 40 is ina transducing relationship with a surface of the magnetic disk 34. Whenthe disk 34 is rotated by the spindle motor 36 the slider is supportedon a thin (typically, 0.05 μm) cushion of air (air bearing) between thesurface of the disk 34 and the air bearing surface (ABS) 48. Themagnetic head 40 may then be employed for writing information tomultiple circular tracks on the surface of the disk 34, as well as forreading information therefrom. Processing circuitry 50 exchangessignals, representing such information, with the head 40, providesspindle motor drive signals for rotating the magnetic disk 34, andprovides control signals to the actuator for moving the slider tovarious tracks. In FIG. 4 the slider 42 is shown mounted to a suspension44. The components described hereinabove may be mounted on a frame 54 ofa housing 55, as shown in FIG. 3.

FIG. 5 is an ABS view of the slider 42 and the magnetic head 40. Theslider has a center rail 56 that supports the magnetic head 40, and siderails 58 and 60. The rails 56, 58 and 60 extend from a cross rail 62.With respect to rotation of the magnetic disk 34, the cross rail 62 isat a leading edge 64 of the slider and the magnetic head 40 is at atrailing edge 66 of the slider.

FIG. 6 is a side cross-sectional elevation view of a merged magnetichead 40, which includes a write head portion 70 and a read head portion72, the read head portion employing a tunnel junction sensor and fluxguide 74 of the present invention. FIG. 7 is an ABS view of FIG. 6. Thetunnel junction sensor and flux guide 74 and an insulation layer 75 maybe sandwiched between first and second lead layers 76 and 78 which, inturn, are sandwiched between ferromagnetic first and second shieldlayers 80 and 82. In response to field signals from the rotating disk,the resistance of the spin valve sensor changes. A tunneling current(I_(T)) conducted through the sensor causes these resistance changes tobe manifested as potential changes. These potential changes are thenprocessed as readback signals by the processing circuitry 50 shown inFIG. 3. The tunneling current (I_(T)) may be conducted through thetunnel junction sensor perpendicular to the planes of its thin filmsurfaces by the first and second shield layers 80 and 82 and the firstand second lead layers 76 and 78. In a piggyback head the second shieldlayer and the first pole piece layer are separate layers which areseparated by a nonmagnetic isolation layer.

The write head portion 70 of the magnetic head 40 includes a coil layer84 which is sandwiched between first and second insulation layers 86 and88. A third insulation layer 90 may be employed for planarizing the headto eliminate ripples in the second insulation layer caused by the coillayer 84. The first, second and third insulation layers are referred toin the art as an “insulation stack”. The coil layer 84 and the first,second and third insulation layers 86, 88 and 90 are sandwiched betweenfirst and second pole piece layers 92 and 94. The first and second polepiece layers 92 and 94 are magnetically coupled at a back gap 96 andhave first and second pole tips 98 and 100 which are separated by awrite gap layer 102 at the ABS. As shown in FIGS. 2 and 4, first andsecond solder connections 104 and 106 connect leads from the spin valvesensor 74 to leads 112 and 114 on the suspension 44, and third andfourth solder connections 116 and 118 connect leads 120 and 122 from thecoil 84 (see FIG. 10) to leads 124 and 126 on the suspension.

Longitudinal cross-sections of two embodiments of the present inventionare illustrated in FIGS. 20 and 31 wherein, in FIG. 20, a magnetic headassembly is shown which has a flux guide at the ABS and a recessedtunnel junction sensor with a top located free layer 212, and FIG. 31shows a magnetic head assembly with a flux guide at the ABS and arecessed tunnel junction sensor with a bottom located free layer 306.The magnetic head assembly in FIG. 20 is made by various steps shown inFIGS. 9-19 and the magnetic head assembly in FIG. 31 is made by varioussteps shown in FIGS. 21-30. In each of the methods of making, as shownin FIGS. 9-19 or FIGS. 21-30, various layers may be formed on a wafer(not shown) by various sputtering techniques, such as ion beamsputtering or magnetron sputtering which are well known in the art,various masks may be formed, such as photoresist masks on the layers,milling may be implemented to remove exposed portions of the layersabout the mask and the mask is then removed. The mask may be formed byfirst spinning a layer of photoresist on the layers, exposing thephotoresist mask to light in areas that are to be removed, assuming thatthe photoresist is a positive photoresist, and then exposing thephotoresist to a developer which removes the exposed portions of themask.

In a preferred embodiment of each method, bilayer photoresist masks areemployed wherein each bilayer photoresist mask has top and bottomportions with the bottom portion being recessed with respect to the topportion. This type of mask is formed by spinning bottom and topphotoresist layers on the wafer wherein the bottom layer has apreferential dissolution rate with respect to the top photoresist layer.The top photoresist layer has a preferential exposure to light imagingwith respect to the bottom photoresist layer. After light imaging thelayers, a developer removes the light imaged portion of the topphotoresist layer and then preferentially dissolves the bottomphotoresist layer causing an undercut below the top photoresist layer.After the bilayer photoresist is formed, milling, such as ion milling,is employed for removing all exposed portions of layers about thebilayer photoresist mask, one or more layers of desired materials arethen deposited about the mask as well as on top of the mask and then themask is subjected to a developer which dissolves the bottom photoresistlayer of the bilayer mask resulting in the mask being lifted off thewafer along with deposited layers formed thereon. It should beunderstood that a plurality of magnetic head assemblies are typicallyformed in rows and columns on a wafer by the above techniques afterwhich the wafer is diced into rows of magnetic head assemblies. Each rowof magnetic head assemblies is then lapped to the air bearing surfaceand each row of magnetic head assemblies is then diced into individualmagnetic head assemblies. The magnetic head assemblies are then mountedon suspensions for use in a magnetic disk drive. The methods describedhereinbelow illustrate the fabrication of individual magnetic headassemblies out of a plurality of such magnetic head assemblies in theaforementioned rows and columns.

First Method of the Present Invention

In FIG. 9 a plurality of sensor material layers 200 are formed on awafer (not shown). The sensor material layers may include a first shieldlayer (S1) 202, which may be the same as the first shield layer 80 inFIGS. 6 and 7, a first lead layer (L1) 204, an antiferromagnetic (AFM)pinning layer 206, a pinned layer (P) 208, a barrier layer (B) 210, afirst free layer (F1) 212 and a cap layer 214, such as tantalum (Ta),for protecting the layers therebelow from subsequent processing steps.In FIG. 10 a first bilayer photoresist mask 216 is formed on top of thecap layer 214 for defining a stripe height of the sensor. In FIG. 11 thesensor material layers exposed about the mask 216 are removed down tothe first shield layer 202 and then the wafer is backfilled with alumina(AL₂O₃). The thickness of the alumina layer 218 in FIG. 11, such as 200Å, is less than the total thickness, such as 275 Å, of the milled-awaysensor material layers comprising the first lead layer 204, the pinninglayer 206, the pinned layer 208, the barrier layer 210, the free layer212 and the cap layer 214. This is important for reducing the gapbetween the first shield layer 202 and a second shield layer at the ABS,as compared to a gap between the first shield layer 202 and the secondshield layer at the sensor, which will be described in more detailhereinafter. After removing the first mask 216, the wafer is subjectedto sputter etching which removes a portion of the first free layer 212and portions of the backfilled alumina layer 218, as shown in FIG. 12. Asecond free layer (F2) 220, a longitudinal bias stack (LBS) 221 and asecond lead layer (L2) 222 are then formed on the wafer, as shown inFIG. 13. Exemplary embodiments of the LBS are illustrated in FIGS. 32,33 and 34.

A second bilayer photoresist mask 224 is then formed on the wafer withopenings 226 and 228 for defining a track width of the sensor, as shownin FIG. 14. Ion milling (IM) is then implemented to remove exposedportions of the sensor material layers in the openings 226 and 228 downto the first lead layer 204, as shown in FIG. 15, or optionally justpassing the barrier layer 210, and then the wafer is backfilled with analumina layer 230. As shown in FIG. 16, the second mask 224 is removedand then a second shield layer (S2) 232 is formed on the wafer which maybe the same as the second shield layer 82 shown in FIGS. 6 and 7.

In FIG. 17 a third bilayer photoresist mask 234 is formed on the secondshield layer 232 for defining a back edge 236 of the flux guide. Asshown in FIGS. 18 and 20, ion milling is implemented to remove exposedportions of the sensor material layers down to the first shield layer202 and then the third mask 234 is removed. In FIG. 19 the wafer islapped to the ABS which defines the front edge of the flux guide. Alongitudinal cross-section of the resulting flux guide and recessedsensor are illustrated in FIG. 20. It can be seen in FIG. 20 that thedistance between the first and second shield layers 202 and 232 at theABS is less than the distance between the first and second shield layersat the sensor.

Second Method of the Present Invention

In FIG. 21 a plurality of sensor material layers 300 are formed on thewafer (not shown). The sensor material layers 300 may include a firstshield layer (S1) 302, which is the same as the first shield layer 80shown in FIGS. 6 and 7, a first lead layer (L1) 304, a longitudinal biasstack (LBS) 305, a free layer (F) 306, a barrier layer (B) 308, a pinnedlayer (P) 310, an antiferromagnetic (AFM) layer 312 and a cap layer 314.

In FIG. 22 a first bilayer photoresist mask 316 is formed on the caplayer 314 for defining a back edge 318 of the flux guide. In FIG. 23 thewafer is ion milled (IM) to remove all portions of the sensor materiallayers about the mask 316 which passes the barrier layer 310, an aluminalayer 320 has been formed and the first mask 316 has been removed. Theresulting structure is illustrated in FIG. 24.

In FIG. 25 a second bilayer photoresist mask 322 has been formed withopenings 324 and 326 for defining a track width (TW) of the sensor andflux guide. As shown in FIG. 26, ion milling (IM) is then employed forremoving all exposed portions of the sensor material layers passing atleast the barrier layer 310 and optionally down to the first shieldlayer 302. The wafer is then backfilled with an alumina layer (Al₂O₃)328.

In FIG. 27 a third bilayer photoresist mask 330 is formed on the waferfor defining the stripe height of the sensor. In FIG. 28 ion milling(IM) is implemented for removing exposed sensor material layers down tothe free layer 306 and the wafer is then backfilled with an aluminalayer 332 which has a thickness that is less than a total thickness ofthe barrier layer 308, the pinned layer 310, the pinning layer 312 andthe cap layer 314. This reduced thickness is key to reducing the gapbetween first and second shield layers at the ABS, as compared to thegap between the first and second shield layers at the sensor, which isdescribed hereinafter.

In FIG. 29 the third mask 330 is removed and a second lead layer (L2)334 and a second shield layer (S2) 336 are formed on the wafer, as shownin FIG. 31. In FIG. 30 the wafer is lapped to the ABS which defines afront edge 338 and stripe height of the flux guide as well as the ABS. Alongitudinal cross-sectional view through the resulting structure isillustrated in FIG. 31 which shows that the distance between the firstand second shield layers 302 and 336 at the ABS is less than thedistance between the first and second shield layers 302 and 336 at thesensor. This reduced gap increases the linear bit read density of theread head. It should also be noted that the flux guide and the sensorhave a common free layer 306 with the free layer portion between the ABSand the sensor serving as a flux guide for conducting field signals fromthe rotating magnetic disk to the free layer portion in the sensor.

Longitudinal Biasing Stacks (LBS)

FIGS. 32, 33 and 34 illustrate various embodiments of the longitudinalbias stack (LBS) 221 which may be employed in the read head embodimentshown in FIG. 20. FIG. 32 shows a first embodiment of the LBS 221 whichhas a hard bias layer (HB) 400 and a nonmagnetic spacer layer 402 whichmay be Ta. The spacer layer 402 is located between the hard bias layer400 and the one or more free layers in FIG. 20. In this embodiment thehard bias layer 400 exerts a field from its ends to magnetostaticallybias the free layer(s) parallel to the ABS. A second embodiment of theLBS 221, which is illustrated in FIG. 33, is the same as the embodimentshown in FIG. 32 except a ferromagnetic pinning layer (P) 404 is locatedon the spacer layer 402 and an antiferromagnetic (AFM) pinning layer 406is located on and exchange coupled to the pinned layer. The pinninglayer 406 pins a magnetic moment 408 of the pinned layer parallel to theABS and parallel to the major thin film planes of the layers with amagnetic moment 410 of the free layers 212 and 220 in FIG. 20 pinnedantiparallel to the magnetic moment 408, in the same manner as describedhereinabove. The embodiment of the LBS 221 shown in FIG. 34 is the sameas the bias stack shown in FIG. 33 except a ruthenium (Ru) layer 414 issubstituted for the tantalum (Ta) spacer layer 402. The Ru layer 414 issufficiently thin (i.e. 8 Å) to cause an antiparallel coupling betweenthe pinned layer 404 and the one or more free layers. It should beunderstood that a reverse order of the layers of the LBS 221 shown inFIGS. 32, 33 and 34 is employed for various embodiments of the LBS 305shown in FIG. 31.

Discussion

It should be understood that in each of the embodiments the first andsecond lead layers (L1) and (L2) may be omitted with the first andsecond shield layers (S1) and (S2) serving as first and second leads forconducting a tunneling current through the sensor material layersperpendicular to their thin film planes. It should also be understoodthat the barrier layer (B) in each of the embodiments may be a spacerlayer which is formed from a nonmagnetic conductive material such ascopper. Either type of sensor is a current perpendicular to the plane(CPP) type of spin valve sensor. The ferromagnetic layers may beconstructed of a material such as nickel iron (NiFe) and theantiferromagnetic pinning layer may be constructed of a conductiveantiferromagnetic material such a nickel manganese (NiMn). It shouldfurther be understood that in lieu of depositing alumina layers 230 and328 in FIGS. 15 and 26 a very thin alumina layer (not shown) may bedeposited followed by depositing a hard bias layer (not shown) on eachside of the sensor for longitudinally biasing and stabilizing the freelayer of the sensor. It should also be understood that other materialsmay be used in place of the alumina, such as silicon dioxide (SiO₂).

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

1. A magnetic head assembly having an air bearing surface (ABS)comprising: a read head including: first and second ferromagnetic shieldlayers; a read sensor recessed from the ABS and which includes aferromagnetic free layer; a ferromagnetic flux guide magneticallyconnected to the read sensor and extending from the read sensor to theABS for conducting field signals to the read sensor; each of the readsensor and the flux guide being located between ferromagnetic first andsecond shield layers; a distance between the first and second shieldlayers at the ABS being less than a distance between the first andsecond shield layers at the read sensor; and a longitudinal biasingstack (LBS) magnetically coupled to the free layer for biasing amagnetic moment of the free layer parallel to the ABS and parallel tomajor planes of the layers; the LBS including: a hard bias layer; and anonmagnetic metal spacer layer located between and interfacing the freelayer and the hard bias layer; each of the free layer, hard bias layerand spacer layer having top and bottom large surfaces which are boundedby front and rear surfaces and first and second side surfaces whereinthe front surfaces form a portion of the ABS and each of the top andbottom large surfaces has a larger surface area than each of the frontand rear surfaces and each of the first and second side surfaces and isperpendicular thereto; and each of the top and bottom large surfaces ofthe spacer layer interfacing a respective large surface area of the freelayer and the hard bias layer.
 2. A magnetic head assembly as claimed inclaim 1 further comprising: the flux guide including an extension of thefree layer which extends from the sensor to the ABS; the read sensorfurther including: a ferromagnetic pinned layer that has a magneticmoment; an antiferromagnetic pinning layer exchange coupled to thepinned layer for pinning the magnetic moment of the pinned layer; and aspacer layer located between the pinned layer and said free layer; andsaid pinned layer, pinning layer and spacer layer being located only insaid read sensor.
 3. A magnetic head assembly as claimed in claim 2wherein the spacer layer is a nonmagnetic electrically nonconductivebarrier layer.
 4. A magnetic head assembly having an air bearing surface(ABS) comprising: a read head including: first and second ferromagneticshield layers; a read sensor recessed from the ABS and which includes aferromagnetic free layer; a ferromagnetic flux guide magneticallyconnected to the read sensor and extending from the read sensor to theABS for conducting field signals to the read sensor; each of the readsensor and the flux guide being located between ferromagnetic first andsecond shield layers; a distance between the first and second shieldlayers at the ABS being less than a distance between the first andsecond shield layers at the read sensor; and a longitudinal biasingstack (LBS) magnetically coupled to the free layer for biasing amagnetic moment of the free layer parallel to the ABS and parallel tomajor planes of the layers; the LBS including: a hard bias layer; and anonmagnetic metal spacer layer located between and interfacing the freelayer and the hard bias layer; the read sensor having a sensor stripeheight and the flux guide having a flux guide stripe height; anddielectric layers electrically insulating some of the layers of the readhead along the flux guide stripe height except along the sensor stripeheight.
 5. A magnetic head assembly as claimed in claim 4 furthercomprising: each of the free layer, hard bias layer and spacer layerhaving top and bottom large surfaces which are bounded by front and rearsurfaces and first and second side surfaces wherein the front surfacesform a portion of the ABS and each of the top and bottom large surfaceshas a larger surface area than each of the front and rear surfaces andeach of the first and second side surfaces and is perpendicular thereto;and each of the top and bottom large surfaces of the spacer layerinterfacing a respective large surface area of the free layer and thehard bias layer.
 6. A magnetic head assembly as claimed in claim 4further comprising: the flux guide including an extension of the freelayer which extends from the sensor to the ABS; the read sensor furtherincluding: a ferromagnetic pinned layer that has a magnetic moment; anantiferromagnetic pinning layer exchange coupled to the pinned layer forpinning the magnetic moment of the pinned layer; and a spacer layerlocated between the pinned layer and said free layer; and said pinnedlayer, pinning layer and spacer layer being located only in said readsensor.
 7. A magnetic head assembly as claimed in claim 6 wherein thespacer layer is a nonmagnetic electrically nonconductive barrier layer.8. A magnetic disk drive that has a magnetic head assembly which has anair bearing surface (ABS) and a read head and a write head, the magneticdisk drive comprising: the read head including: first and secondferromagnetic shield layers; a read sensor recessed from the ABS andwhich includes a ferromagnetic free layer; a ferromagnetic flux guidemagnetically connected to the read sensor and extending from the readsensor to the ABS for conducting field signals to the read sensor; eachof the read sensor and the flux guide being located betweenferromagnetic first and second shield layers; a distance between thefirst and second shield layers at the ABS being less than a distancebetween the first and second shield layers at the read sensor; and alongitudinal biasing stack (LBS) magnetically coupled to the free layerfor biasing a magnetic moment of the free layer parallel to the ABS andparallel to major planes of the layers; the LBS including: a hard biaslayer; and a nonmagnetic metal spacer layer located between andinterfacing the free layer and the hard bias layer; each of the freelayer, hard bias layer and spacer layer having top and bottom largesurfaces which are bounded by front and rear surfaces and first andsecond side surfaces wherein the front surfaces form a portion of theABS and each of the top and bottom large surfaces has a larger surfacearea than each of the front and rear surfaces and each of the first andsecond side surfaces and is perpendicular thereto; and each of the topand bottom large surfaces of the spacer layer interfacing a respectivelarge surface area of the free layer and the hard bias layer; the writehead including: ferromagnetic first and second pole piece layers thathave a yoke portion located between a pole tip portion and a back gapportion; a nonmagnetic write gap layer located between the role tipportions of the first and second pole piece layers; an insulation stackwith at least one coil layer embedded therein located between the yokeportions of the first and second pole piece layers; and the first andsecond pole piece layers being connected at their back gap portions; ahousing; a magnetic disk rotatably supported in the housing; a supportmounted in the housing for supporting the magnetic head assembly withsaid ABS facing the magnetic disk so that the magnetic head assembly isin a transducing relationship with the magnetic disk; a spindle motorfor rotating the magnetic disk; an actuator positioning means connectedto the support for moving the magnetic head assembly to multiplepositions with respect to said magnetic disk; and a processor connectedto the magnetic head assembly, to the spindle motor and to the actuatorpositioning means for exchanging signals with the magnetic headassembly, for controlling movement of the magnetic disk and forcontrolling the position of the magnetic head assembly.
 9. A magneticdisk drive as claimed in claim 8 further comprising: the flux guideincluding an extension of the free layer which extends from the sensorto the ABS; the read sensor further including: a ferromagnetic pinnedlayer that has a magnetic moment; an antiferromagnetic pinning layerexchange coupled to the pinned layer for pinning the magnetic moment ofthe pinned layer; and a spacer layer located between the pinned layerand said free layer; and said pinned layer, pinning layer and spacerlayer being located only in said read sensor.
 10. A magnetic disk driveas claimed in claim 9 wherein the spacer layer is a nonmagneticelectrically nonconductive barrier layer.
 11. A magnetic disk drive thathas a magnetic head assembly which has an air bearing surface (ABS) anda read head and a write head, the magnetic disk drive comprising: theread head including: first and second ferromagnetic shield layers; aread sensor recessed from the ABS and which includes a ferromagneticfree layer; a ferromagnetic flux guide magnetically connected to theread sensor and extending from the read sensor to the ABS for conductingfield signals to the read sensor; each of the read sensor and the fluxguide being located between ferromagnetic first and second shieldlayers; a distance between the first and second shield layers at the ABSbeing less than a distance between the first and second shield layers atthe read sensor; and a longitudinal biasing stack (LBS) magneticallycoupled to the free layer for biasing a magnetic moment of the freelayer parallel to the ABS and parallel to major planes of the layers;the LBS including: a hard bias layer; and a nonmagnetic metal spacerlayer located between and interfacing the free layer and the hard biaslayer; the read sensor having a sensor stripe height and the flux guidehaving a flux guide stripe height; and dielectric layers electricallyinsulating some of the layers of the read head along the flux guidestripe height except along the sensor stripe height; the write headincluding: ferromagnetic first and second pole piece layers that have ayoke portion located between a pole tip portion and a back gap portion;a nonmagnetic write gap layer located between the pole tip portions ofthe first and second pole piece layers; an insulation stack with atleast one coil layer embedded therein located between the yoke portionsof the first and second pole piece layers; and the first and second polepiece layers being connected at their back gap portions; a housing; amagnetic disk rotatably supported in the housing; a support mounted inthe housing for supporting the magnetic head assembly with said ABSfacing the magnetic disk so that the magnetic head assembly is in atransducing relationship with the magnetic disk; a spindle motor forrotating the magnetic disk; an actuator positioning means connected tothe support for moving the magnetic head assembly to multiple positionswith respect to said magnetic disk; and a processor connected to themagnetic head assembly to the spindle motor and to the actuatorpositioning means for exchanging signals with the magnetic headassembly, for controlling movement of the magnetic disk and forcontrolling the position of the magnetic head assembly.
 12. A magneticdisk drive as claimed in claim 11 further comprising: each of the freelayer, hard bias layer and spacer layer having top and bottom largesurfaces which are bounded by front and rear surfaces and first andsecond side surfaces wherein the front surfaces form a portion of theABS and each of the top and bottom large surfaces has a larger surfacearea than each of the front and rear surfaces and each of the first andsecond side surfaces and is perpendicular thereto; and each of the topand bottom large surfaces of the spacer layer interfacing a respectivelarge surface area of the free layer and the hard bias layer.
 13. Amagnetic disk drive as claimed in claim 11 further comprising: the fluxguide including an extension of the free layer which extends from thesensor to the ABS; the read sensor further including: a ferromagneticpinned layer that has a magnetic moment; an antiferromagnetic pinninglayer exchange coupled to the pinned layer for pinning the magneticmoment of the pinned layer; and a spacer layer located between thepinned layer and said free layer; and said pinned layer, pinning layerand spacer layer being located only in said read sensor.
 14. A magneticdisk drive as claimed in claim 13 wherein the spacer layer is anonmagnetic electrically nonconductive barrier layer.